Application of Soy Protein in Flour Products
Abstract: Soy protein is a kind of plant protein with good amino acid balance. It is rich in 8 essential amino acids required by the human body. It is basically in line with the amino acid composition recommended by the World Health Organization and the World Food and Agriculture Organization; the digestibility of protein—corrected amino acids When the score (PDCAAS) is used to express the quality of protein, soy protein and animal protein are the same; compared with animal protein, soy protein has a health care effect on the kidneys. Substituting soy protein for animal protein can reduce the excretion of calcium in the urinary system. In 1999, the U.S. Food and Drug Administration (FDA) recognized that soy protein can lower cholesterol. In recent years, there have also been reports that soy protein has health-care functions such as lowering blood lipids, lowering blood pressure, and lowering blood sugar.
Keywords: Soy protein, flour products, application
Application in steamed bread
The nutritional value of steamed buns is low, and the shelf life after steaming is generally no more than 3 days. However, traditional low-temperature storage will significantly reduce the quality and sensory evaluation of steamed buns. Appropriate addition of soy protein in the steamed bread can not only increase the nutritional value of the steamed bread, but also increase the volume, sensory quality and shelf life of the steamed bread, while excessive addition will reduce the quality of the steamed bread. Gao Xueqin et al. found that adding 10% soy protein powder to steamed buns can increase the volume of steamed buns, improve the chewiness of steamed buns, and improve the internal quality of steamed buns. Oxidation can strengthen wheat gluten. Research by He Yaqiang and others found that adding 3% soy protein isolate powder to wheat flour can increase the volume, specific volume and comprehensive score of steamed bread, and make the surface of steamed bread white, smooth, symmetrical, spherical, and have fine and uniform internal pores. , Toughness and viscosity increase, etc. Li Liangliang et al. found that the addition of 2% soy protein isolate has a significant improvement effect on the starch retrogradation of frozen steamed buns and delays the trend of quality decline during the storage of steamed buns. Under the same conditions, the two groups of steamed buns with 4% and 6% soy protein isolate added, the iodine color value was close to or lower than the control group (not added soy protein isolate steamed buns group), which may be due to excessive addition of soy protein isolate, soy protein isolate There are partial cross-links between the hydrogen bonds in the starch molecule and the hydrogen bonds in the starch molecule, which reduces the soluble amylose content. Although the addition of soy protein can improve the overall quality of steamed bread, similar effects have not been achieved in the preservation of steamed bread. If this bottleneck can be overcome, it is believed that the application of soy protein in steamed bread will be more extensive. However, soy protein powder does not contain gluten protein, and excessive addition will hinder the formation of gluten network. According to foreign reports, in the process of gluten formation, soy protein and wheat gliadin are combined in a hydrophobic manner to form a wheat gliadin-soy protein-wheat gluten complex. This complex will make steamed bread difficult to swell and become smaller. .
Application in bread
Appropriate addition of soy protein to bread can improve the nutrition, sensory quality and volume of bread, and improve the flavor and baking quality of bread.
Soy protein added to bread that is widely consumed is an effective means to improve human health. For this reason, the researchers replaced 20% and 12% of wheat flour with soy protein powder and soy protein isolate in the bread production process, and used bread without soy protein powder or soy protein isolate as a reference, and then a well-trained evaluation team Conduct sensory evaluation. The results showed that there was no significant difference in flavor, texture, hardness, etc. between the bread with soy protein powder and the control group, while the bread with soy protein isolate had poorer overall quality, which was mainly manifested in poor texture and chewiness, soy Big fishy smell, high hardness and viscosity, which may be due to the high content of protein, daidzein, genistein and isoflavones in soy protein isolate. Therefore, adding 20% soy protein powder can not only increase the protein content of bread, but also will not affect the overall flavor and texture of bread, which has good application prospects.
Researchers added 6% soy protein powder to bread, and the sensory evaluation score of bread was increased from 40.2 to 52.2, and the absorption of iron, calcium, zinc and other minerals in the body would not have a negative impact, while adding 6% Whey protein can increase the absorption of calcium, but weaken the absorption of iron and zinc. In addition, the addition of whey protein will reduce the titer of lysine in the bread. If soy protein powder is added at the same time, the loss of lazy acid titer can be alleviated. Researchers used steamed and roasted soybean flour as the main raw material to make bread, and studied the physical and chemical properties and sensory properties of soybean bread. The research results show that the pretreatment of soy flour can not only increase the volume of bread, but also relieve the unhealthy beany taste of soy bread. Researchers studied the effects of protein powders made from germinated and non-germinated soybeans on the rheological properties of the dough and the quality of the bread. They believed that the volume and color of the bread with two protein powders (additions of 0.5%, 1.0%, 1.5%) were added. All have been improved, and the color of the crust has not changed much. The evaluation result of the texture of the bread with added soybean protein powder is similar to or better than that of the bread without addition. Finally, through experimental comparison, it is found that the germinated soy protein powder can improve the baking properties of the dough more than the non-germinated soy protein powder. Research by Yang Chunhua et al. found that adding 3% soy 11S globulin to wheat flour can improve the rheological properties of the dough and also improve the strength and elasticity of the bread. The reason is that soy protein is a good baker’s yeast. Therefore, adding an appropriate amount of soy protein products can make the dough ferment vigorously, so as to achieve the purpose of improving the quality of bread.
Application in noodles
Noodles are a traditional staple food that is simple to make and convenient to eat. High-quality finished noodles should be bright in color, slow to change color, have a long shelf life, have no visible microbial degradation and oxidative rancidity, and have appropriate flavor and texture. Relevant studies have shown that the level of protein content is highly related to the color and texture of noodles. A reasonable protein content is of great significance to the pursuit of chewy Chinese-style noodles.
Generally speaking, the content of gluten determines the performance of noodles and dough. The higher the gluten content, the better the toughness, elasticity and extensibility of the dough, and the lower the rate of broken noodles during cooking and smoothness. And chewiness is better. The researchers added different substances to the four groups of 95g wheat flour. The additions are as follows; one group adds 5g soy protein isolate; one group adds soy protein isolate and ribose; one group adds soy protein isolate and transglutaminase; the other group adds Soy protein isolate, ribose and transglutaminase. The results show that the last group of noodles can be catalyzed by transglutaminase and treated with ribose to control the texture and starch hydrolysis of the noodles. These properties may be due to the formation of r-glutamyllysine bonds and the ribose-induced Mela during the cooking German reaction. In addition, the noodles with soy protein isolate, transglutaminase and ribose added have a lower blood glucose index after consumption and the noodles have a stronger texture. Feng Lei et al. found that when 20% soy protein powder is added to noodles, the dry matter loss rate of noodles is the lowest. This is because soy protein has good water retention properties, which can improve the mechanical resistance of the dough and increase the stability time of the dough. As the content of soy flour continues to increase, the dilution effect of soy protein on the gluten structure is not conducive to the formation of gluten, leading to an increase in the loss of starch and protein in the noodles.
Due to the specific functional properties of soy protein, soy protein can reduce the noodle breakage rate, dry matter loss, and improve the processing performance of the dough. However, in the process of noodle processing, the specific mechanism of soy protein’s gluten formation from wheat protein needs further study.
Application in other noodle products
Foreign scholars have verified that instant noodles with active soy protein powder have a good taste, a special fragrance when chewing, good palatability, strong toughness, a significant decrease in the brittleness of the noodles, and a faster rehydration during cooking. This is due to the fact that soy protein has a The characteristic of gelling, its viscosity increases with the increase of its concentration.
Dumpling noodles are mainly composed of wheat flour. The characteristics of wheat flour are an important factor affecting the quality of dumplings. High-quality dumplings should have the characteristics of white and bright color, good softness, strong elasticity, low viscosity and smooth texture. Liang Ling et al. found that adding 20g of soy protein to 1kg of wheat flour can significantly improve the sensory quality of frozen dumplings. This may be because soy protein is an amphoteric substance, which can interact with polar and non-polar groups in wheat flour. The hydrophilic polar side chain binds to water and retains moisture; secondly, it is because soy protein enhances gluten. Network structure.
Problems and prospects
In recent years, with the continuous in-depth study of soy protein, the nutritional value of soy protein and its health care functions for relieving obesity, high cholesterol, osteoporosis, cancer and other diseases have gradually become known to people. If soy protein is introduced into people’s staple food such as steamed buns and noodles, it will not only obtain higher nutritional value at a lower price, but also improve the quality of the noodle products. However, the application of functional foods has not attracted widespread attention from food science and technology workers. In addition, the application of soy protein in small-scale noodle products such as instant noodles, dumpling wrappers, biscuits, pancakes, glutinous rice balls, shrimp crackers, etc. is less and not in-depth. In today’s society, people’s diets are diversified. Researchers should not only be limited to studying a few common noodle products, but should consciously expand the scope of research and develop more diverse, nutritious, healthy and safe noodle snacks to satisfy different groups of people. Hobby.
At present, the development of soybean protein is not deep enough. The main reasons are: 1) backward development equipment and insufficient capital investment; 2) my country’s soybean protein development technology is not mature enough. I believe that with the continuous in-depth research of food science and technology workers in the next ten years, we will be able to develop soy protein modification technology suitable for noodle products, and develop more noodle foods suitable for different groups of people. The application of soy protein in noodle products The prospects will be broader.